Severe gastric distention was observed in rats 20 hours after undergoing partial hepatectomy surgery under isoflurane anesthesia and receiving buprenorphine (0.3 mg/kg) post-operatively. Hardwood bedding comprised the bulk of the gastric contents. A study was undertaken to determine the cause for the bedding ingestion and gastric distention. Male, Sprague-Dawley rats, 10 weeks of age were assigned to one of five groups. Group 1 (n=6) underwent a laparotomy using isoflurane anesthesia with buprenorphine (0.3 mg/kg) administered post-operatively. Group 2 (n=6) underwent a laparotomy using isoflurane anesthesia with buprenorphine (0.05 mg/kg) administered post-operatively. Group 3 (n=5) received isoflurane anesthesia followed by buprenorphine (0.3 mg/kg). Group 4 (n=6) received buprenorphine (0.3 mg/kg) only. Group 5 (n=18) received isoflurane anesthesia only. Isoflurane was administered at the same rate, concentration, and duration for all groups (Groups 1,2,3,5). Buprenorphine was administered subcutaneously as a single injection when anesthesia was discontinued (Groups 1-4). Rats were housed singley in polycarbonate cages with hardwood bedding. Rodent chow and water were offered ad libitum. Food and water consumption was assessed over the post-treatment period. Eighteen to 20 hours after treatment, rats were euthanized, stomachs with contents weighed, contents examined grossly, and wet and dry gastric content weights recorded. All weights were significantly elevated in rats receiving buprenorphine (Groups 1-4) when compared to rats receiving isoflurane only (Group 5). Hardwood bedding comprised the bulk of the gastric contents in groups receiving buprenorphine while the stomach of rats receiving isoflurane contained rodent chow with little or no hardwood bedding. These results indicate that a single injection of buprenorphine, at a dose of 0.05 mg/kg or 0.3 mg/kg, induce rats to ingest hardwood bedding leading to gastric distention. It was concluded that buprenorphine should be used with caution in studies evaluating gastric parameters in rats.